BIOL 111 Lecture Notes - Bronchiole, Dorsal Nerve Cord, Viviparity

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Published on 26 Jun 2012
School
McGill University
Department
Biology (Sci)
Course
BIOL 111
Professor
Bio 111 Alanna Houston
November 13, 2007
-The first fish were jawless and they were benthic
oHad bony plates
oHeavily armoured
oSmall
oOstracoderms (shell skin)
-Later, the fish were bigger, spiny-finned, jawed predator,
ancanthodians (spiny fin)
-Later, fish were less armoured, large predators = placoderms
(plate skin)
-Early marine predators preying on fish
oSea scorpions
THE RISE TO LAND
Why move on land?
-Devonian droughts
oShallow inland seas, swamps, ponds, experience low DO2
-Competition in water
oCrowding in shallow pools
-Insects and plants on land
-No vertebrate predators
Major Physical Differences between land and water
-availability of water
-density of medium
-amount of oxygen (most important)
-stability of temperature
-amount of UV radiation
Advantages of Terrestrial respiration
-Air has higher concentration of oxygen than water
-Gases diffuse faster in air than water
-Air is less dense so less energy required to move it across
respiratory surfaces
-Lungs evolved early in fish groups. Gas bladder used as
supplementary respiratory organ, then later modified for
buoyancy
Early Gas Bladders
-present in early fish (placoderms – now extinct)
-used as a supplementary respiratory organ
ogulp at air surface
-reappeared in bony fishes
oactinopterygians (ray-finned)
osarcopterygians (lobe-finned)
-Ray-finned fishes
oFrom single dorsal pocket off esophagus
oEvolved into a swim bladder or supplementary respiratory
device
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Bio 111 Alanna Houston
oGland that releases lactic acid that increases acidity of the
blood and causes O2 to be released by the hemoglobin so
that it is oxygen that fills the gas bladder
o
-Lobe-finned fishes
oFrom paired ventral pockets off esophagus
oEvolved into a supplemental respiratory device
o
-The embryonic origin of the gas bladder was from the digestive
tract (endoderm)
Problems on Land:
-Dessication
oNeed to stay moist
oMost require water for fertilization and larval development
-Air is less dense than water
oRequire stronger skeletal support, muscles
oRequire more energy, more O2 brought in and distributed
-Air temperature is more variable
oBody temperature will fluctuate more
oNeed to modify behaviour or physiology
-UV radiation more intense on land
oNeed physical protection or change behaviour
-A lobe-finned bony fish is the most direct ancestor to tetrapods
oDeclined after Permian extinction
oOnly 8 extant species
oCommon during Devonian period
Direct ancestor to tetrapods
-Rhipidistian fish
-Internal nostrils (nares)
-Teeth
-Appendages similar to tetrapods
-Best known fossil from Gaspe, Quebec
Closest extant fish
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Bio 111 Alanna Houston
-Lungfish
-6 species
-walk on lobe-fins
otetrapod motion
-breathe through gills and primitive lung
-estivate in mud during drought
-make a mucous cocoon
Coelacanth – A living fossil
-thought to be extinct
-1930 – found at African fish market
oMarjorie Courtenay Latimer
-1952- 2nd specimen found
-Comoros Islands (East African Coast)
-2nd species discovered in Indonesia – 1998
Early Tetrapods
-Stronger limbs and girdles, vertebral column, ribs
-Tail used for balance, not swimming
-Lungs were primary respiratory organ
-External and internal nostrils
-
Late Devonian life
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Document Summary

The first fish were jawless and they were benthic. November 13, 2007: had bony plates, heavily armoured, small, ostracoderms (shell skin) Later, the fish were bigger, spiny-finned, jawed predator, ancanthodians (spiny fin) Later, fish were less armoured, large predators = placoderms (plate skin) Early marine predators preying on fish: sea scorpions. Competition in water: shallow inland seas, swamps, ponds, experience low do2, crowding in shallow pools. Amount of oxygen (most important) stability of temperature. Air has higher concentration of oxygen than water. Gases diffuse faster in air than water. Air is less dense so less energy required to move it across respiratory surfaces. Gas bladder used as supplementary respiratory organ, then later modified for buoyancy. Present in early fish (placoderms now extinct) Used as a supplementary respiratory organ: gulp at air surface reappeared in bony fishes, actinopterygians (ray-finned, sarcopterygians (lobe-finned, from single dorsal pocket off esophagus, evolved into a swim bladder or supplementary respiratory.

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